Extracellular signal regulated kinases, ERK1/2 and ERK5, are activated by asbestos fibers in mesothelial and airway epithelial cells and play critical roles in cell survival. ERK1/2-dependent Fra-1 expression is also linked causally to morphologic transformation of rat mesothelial cells and expression of genes (c-met, cd44) stimulating cell proliferation and migration. We hypothesize that activation of ERK1/2 and ERK5 signaling pathways occur by carcinogenic fibers (asbestos, erionite) in the pathogenesis of human malignant mesothelioma (MM) and are potentiated by SV40 in a co-carcinogenic manner. Recent exciting data also suggest that these survival pathways are activated in MMs after exposure to chemotherapeutic drugs and can be manipulated to achieve increased cell killing. Thus, we also hypothesize that ERK1/2 and ERK5 pathways contribute, alone or cooperatively, to MM cell survival after chemotherapy. In Aim 1, we will test crocidolite and chrysotile asbestos, well-characterized Turkish erionite (see Project 1), and their nonfibrous analogs, alone and with co-exposures to SV40 to determine if ERK1/2, and ERK5 activity, fos/jun family members, and AP-1 transactivation correlate with patterns of transformation and carcinogenicity as determined in the in vitro/in vivo models developed by Dr. Carbone (Core C). In Aim 2, we will use a panel of SV40+ and - MMs from Core B to determine the effects of dominant negative constructs and small hairpin (sh) RNA interference (RNAi) vectors targeting ERK1/2 and ERK5 on parameters of in vitro cell transformation and survival after treatment with Carmustine (BCNU). In collaboration with Dr. Testa (Project 3) we will also determine if the AKT survival pathway is modified in these studies. In Aim 3, a mouse orthotopic model will be used to determine if SV40+ and - MMs stably transfected with shMEKI, shERKS or both constructs before intrapleural injection and administration of Carmustine, have altered growth and metastases. Identifying the pathways of cell survival in the pathogenesis of MMs is highly significant for prevention and treatment of these devastating tumors. This Program Project allows our previous mechanistic studies in rodent mesothelioma models to be validated in human mesotheliomas and provides us with expertise on virology and MM pathology (Dr. Carbone), AKT survival pathways (Dr. Testa) and use of normal human mesothelial and MM cells (Dr. Pass).